A solar power inverter can be electrically connected to a local load (e.g., an industrial facility, a commercial building, a residential home, etc.) so as to provide electrical power to the local load. The local load is typically also connected to a utility grid and obtains electrical power that is generated by electrical power generators and that is transmitted across the utility grid. The solar power inverter can also supply electrical power to the utility grid. A portion of the utility grid between the solar power inverter and the electrical power generators may experience a disruption or other event (e.g., a switch opening, a line down, etc.) that results in the interruption of the flow of electrical power. In such an event, the solar power inverter and the local load become an island.
Certain electrical standards (e.g., UL 1741 and IEEE 1547) require solar power inverters to detect an islanding condition and disconnect (stop producing electrical power) within a certain period of time (e.g., two seconds). Such requirements stem at least partially from a need to protect line worker safety. Conventional solar power inverters can detect an islanding condition by using a technique involving two mechanisms. In the first mechanism, if the solar power inverter detects a change in utility grid frequency, the solar power inverter changes its frequency in such a way as to attempt to accentuate that utility grid frequency change. If the solar power inverter can affect the utility grid frequency, then an islanding condition has likely occurred. The second mechanism involves supplying reactive power pulses to the utility grid. If an islanding condition exists, the reactive power pulses will cause a perturbation that activates a positive feedback. Upon detecting an islanding condition, the solar power inverter is required to disconnect within the certain period of time.